Snap switch



W. DUBILIER Feb. 15, 1944.

SNAP SWITCH Filed Jan. '7, 1942 FIG.

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' INVENTOR. (w-m' g g-a- BY flaa v ATTORNEY manna rat. it, 1944 PAT ENT;1

. Sm swircn wnnam Dubilier, New'n cheiie; N. y. Application January 7,1942, Serial No. 425,831

8 Claims. (01. 74-97) The present invention relates to electricalswitches of the snap-action type which 'are adapted to interruptsubstantially large currents upon relatively minute physical applicationof pressure or displacement. More particularly, the invention isconcerned with switches of the type comprising essentially a flat leafspring which has a region adjacent to'a fixedly mounted end thereofbiased or strained internally to give a material displacement of theopposite free end of the spring with a jerk or snap action uponapplication of av relatively small movement or pressure to said strainedregion.

Various types of snap-action switches have been known in the past all ofwhich are defective d have disadvantages in one'or the other respect.Thus, one basic construction, as exempliiied by U. S. Patent 1,215,665to H. Landis, comprises a flat springarranged between two rigid bearingsor abutments in such a manner as to assume a curved or arched position.In such a position the spring is held under tension and may be shiftedin the manner of a toggle by a comparatively small force to a neutralposition from whence, owing to its elasticity, it will proceed by a jerkor snap movement to a position of opposite curvature in the manner of atoggle.

Another construction, as exemplified by U. S. Patent 1,089,167 to G. W.Wacker, comprises a spring blade provided with a longitudinal slot, theportion on one side of the slot being secured rigidly and the portion onthe other side of the slot being bent at its opposite ends so as toassume a curved position from which it may be 1 displaced by theappllcationof a small force to a position of reversed curvature with asnap action in a manner similar to that according to the first-mentionedpatent.

A method of constructing a switch of the firstmentioned type utilizing acurved or arced spring secured or supported at its opposite ends isdisclosed in Patent 1,668,974 to A. J. Mottlau. The latter utilizesadouble-slotted fiat spring to provide a bridging member between the.slots which serves as the actuating. spring member, being curved orarched by deformation by the outer spring portions.

Numerous other snap switches have become known in the past consistingessentially of a longitudinally confined spring normally bowed or archedon one side or the other of its dead center and adapted to be thrownagainst its dead center by means of a suitable connection with apressure applying element such as an actuating plunger or thermalexpansion device or directly by internal strain or displacement causedby heat when using a springer bior multi-sheet metal responsivetotemperature changes.

A basically diflerent type of snap-action device to which the presentapplication has specific reference, as exemplified by U. S. Patent1,4483% to J. A. Spencer; 1,780,758 to H. 'G.-Leupold; 1,849,481 to P.De Langie et al., comprises a leaf spring or blade secured at one endcantilever fashion so as to allow its opposite end to move freelybetween two positions of equilibrium with a snap action. 'I'o-this end,a limited portion or region of the spring nearthe pivoted end thereof,that is, at the side opposite to the freely movable end, is caused tobecome internally biased or slightly buckled in such a manner thatapplicae tion of a small force to said biasedregion will cause the freeend of the-spring to move over'a relatively large distance witha-suddenor snap action from one to an opposite position of equilibrium.

In the construction shown'by U.- S. Patent 1,780,758 the spring isbiased by using a blade which is slit for a considerable part of itslength with the sections or legs thereof being slightly bowed or forcedtowards-each'other and secured in this position by a contact serving asa bridgingmember.

-A major disadvantage ofall snap switches of the above described andsimilar types, especially the construction according to U. S. Patent1,780,758, is the fact that great dimculties are experienced in thequantity production thereof due to the large number of rejections anddespite the use of special assembly tools and other precautions taken.In particular, in the case of the last mentioned pivoted type of switchhaving a limited sensitive or biased region next the'pivot point, thedegree of bowing or forcing together the free ends of the spring bladeis'so minute as to cause substantial variations in the final units and aconsiderable number of defective units which are either completelyunusable or not in compliance with the required tolerance range.

Accordingly, it is an object of the present in vention toprovide a novelsnap-action device which is both simple in construction and easy tomanufacture while, at the'same time, insuring high uniformity inquantity production and accuracy and reliability in operation.

A specific object is to "provide a switch of the above character which,while being highly sensitive and accurate in operation, is of anextremely low weight, especially as regards the movable element 01'Contact so as to substantially prevent accidental operation due to shockor other mechanical forces effecting the same.

These and further objects and advantages of the invention will becomemore apparent from the following detailed description taken withreference to the accompanying drawing forming part of this specificationand wherein:

Figure l is a longitudinal cross-section through a switch embodying theprinciples of the invention; Figure 2 is a perspective view and Figure 3a side view of the switch shown in Figure 1; Figure 4 is a top viewshowing one form of construc tion of the spring actuating member for usein a switch according to the inventio Figure 4-A is section taken online lA-lA of Figure 4; Figures 5 and 5-A are top and side views,respectively, of a modification of an actuating spring according to theinvention; Figures 6 and 6A are top and side views, respectively, ofanother modified actuating spring construction; Figure 7 is across-sectional view of an actuating spring showing a modification ofthe contact element; and Figures 8 and 9 are top and side views,respectively, of still a different type of switch construction inaccordance with the invention.

Like reference numerals identify like parts in the diiferent views ofthe drawing.

Referring to Figuresl to 3, the switch shown comprises essentially acast or molded insulating housing or support i which may be of anysuitable material such as ceramic, Bakelite or similar insulatingcomposition material. Support "I has a cavity for containing the switchports and is formed with opposed longitudinal legs II for supporting ormounting the unit upon a base. Suitable fastening means such as rivetsor screws I 2 are arranged to secure the switch parts against thehousing ID. A first contacting II overlying one end of the actuatingleaf spring II is clamped against the support ID by means of a pair ofscrews i2 passing through holes in lug II and spring l5, thus firmlysupporting and securing one end of the springmember i cantilever fashionand effecting electrical connection between the spring member and theterminal lug projecting from one side of the hous-, ing. A second lug His similarly clamped against the opposite end of support ill by a thirdscrew I! and serves both as a cooperating contact for the spring contacti8 and as a connecting terminal element projecting from the oppositeside of the housing Ill. The actuating spring member I5 is properlyinternally strained or biased in the manner to be described presently topro-- vide a sensitive region adjacent to its pivoted end cooperatingwith a push button I 1 or the like slidably mounted in and projectingabove the top face of the housing and serving to actuate the contact I 6into material displacement with a snap action upon application of aslight mechanical pressure upon button II. An insulating plate ofcardboard, Bakelite'or the like is secured with screws I! to provide abottom protective covering for the switch elements; The spacer I9interposed between lug l3 and plate I. insures proper alignment and firmconnec-: tion between the elements.

The switch shown may be used both as a make and break type. In theformer case the cooperating contact is the inner end of lug I4 and inthe latter case a further contact provided with a suitable solderingterminal or the like may be arranged on the oppositeside of contact ll,as shown in the drawing.

Referring now to the switching spring member proper, more particularlyshown in Figures 4 and 4A, the same comprises essentially a leaf springor blade of suitable material such as spring steel, copper or berylliumbronze or the like provided with a T-shaped aperture comprising acentral longitudinal slot 2 2 having one end terminating in twotransverse slots 23. The portion of the blade between the transverseslots 23 and the adjacent edge is deformed by the provision of a pair ofcrimps or grooves 24 substantially parallel to the slot 22 and locatednear the outer ends of the slots 23 in such a manner as to. provide aslightly buckled or internally biased region near the opposite pivotedend of the blade as indicated at r. The

latter, if slightly depressed by means of push button I! or the like asshown in Figure 1, will cause the free end of the spring carrying thecontact i6 riveted or otherwise connected thereto to move suddenly fromone position to another position of Mounting holes 25 serve for securingthe spring blade to the support or housing by rivets or screws as shownin Figure 1 or in anyother suitable manner. In the drawing, thethickness of leaf spring l5 and contact has been exaggerated forcleamess and ease of illustration.

Among the advantages of a snap-action spring member of theafore-descrlbed type is the reduction of parts by the use of a singleintegral slotted spring element which is biased by a simple crimping ordeforming operation and the resultant increased uniformity'of thecompleted elements, resulting in considerable reduction of the number ofrejections or defective units. Another advantage is the fact that thecontact l6, which is of a diflerent metal from the spring I! such assilver-clad copper, may be limited to a size required by purelyelectrical considerations, thus not only reducing its weight butpreventing impairment of the internal tension or bias of the springmember due to the different thermal expansion co-elficient of the springand contact, respectively, as has been found to be the case in prior artconstructions wherein the contact serves as a bridging member to holdthe legs of the spring in bowed position. Consequently, thecharacteristics of a switch spring constructed in accordance with theinvention will vary little within a wide range of ambient temperaturechanges or due to heat caused by the sparking and arcing between thecontacts, thus insuring high operational stability and increased life ofthe switch.

In the construction according to U. S. Patent 1,780,758, on the otherhand, a relatively heavy bar or strip is secured across to two legs ofthe slotted spring which not only acts as a contact piece but serves tohold the legsof the spring together under tension to produce a biasedregion at the opposite supported end of the spring. For practicalreasons this bar is bent around the spring, thus making its' weightstill heavier. Hence. a heavy weight of this type carried by the freeend of the spring is easily affected by vibrations or outside forcessuch as tion or deceleration when the switch is used on an aircraft orother vehicle, resulting in undesir'able operations of the switch andother drawbacks and defects. Moreover, since this bar is usually of ametal. diiferent from the spring metal, the different thermalcoefliclents of expansion and contraction will between the, bar and thespring resulting not only in loosening or deterioration of theelectrical to the construction equilibrium with a snap actiom a suddenacceleraafiect the joint contact but seriously affecting the tension orbias of. the spring, thereby destroying or materially impairing itsoperating characteristics.

All the aforementioned defects and drawbacks are overcome by the novelmethod and construction according to the present invention wherein theweight of the contact piece, which does not have to hold any parts ordetermine the spring tension or bias condition, may be reduced to aminimum while the tension or bias of the sensitive region is affectedsimply and solely by the groove-like crimp or equivalent deformation ofthe free end of the spring in the manner describedhereinabove. In thisconnection, it will be further evident that with the prior art structureit will be extremely difficult to obtain a uniform bias or tension andoperating spring pressure due to the relatively small force anddisplacement involved in drawing together the legs of the spring,whereas in the case of the invention, due to the considerably simplifiedconstruction and method of producing the spring tension, the tension orbias may be effected with considerably increased consistency anduniformit-y for the reasons that will be obvious from the foregoing.

The reduction of'the contact weight has the further advantage that theswitch will be less sensitive to.external shock or other mechanicalforces liable to cause accidental operations. This is of specialimportance when the switch is used on moving vehicles, such asairplanes, in which case shockspr a sudden acceleration or decelerationmay result in unauthorized operation of the switch contacts due toexcessive weight or inertia.

Referring to Figures and 5-A, there is shown a modified actuating springconstructed in accordance with the principles of the invention.

In'this case, the blade [5 has a pairof para1le1- slots 22' and 22"terminating in enlarged portions. The groovm or crimpsid are arrangedbetween the enlarged portions of the slots and the edge of the blade, asshown. In a construction of th s type a pair of sensitive regions willbe produced near the opposite ends of the slots having an overlappingarea r of increased sensitivity engaged by a push button or otheractuatlng' element.

Referring to Figures 6 and 6-A, there is shown a modification similar toFigure 4 having but a single central crimp or groove 24, arranged be-'tween the slightly enlarged portion of the slot 22 and the edge of bladeI5. A construction of this type is especially suited for the provisionof a pair of contacts l6 and IS" on the opposite sides of the crimp 24'.Contacts l6 and [6" may e ther be used for simultaneously controllingtwo electrical circuits or the contacts may. be connected in series forsingle circuit operation to reduce sparking and arcing.

If due to the grooves or crimps 24 and 24' the end of the leaf springbecomes slightly curved, a contact l6 extending over a larger surface ofthe spring having downturned edges engaging said grooves may beprovided,as shown in Figure 7 to hold the spring in straight or flat position.Alternatively, a contact strip may be used extending over theentire.,width of the spring if the we ght of the contact is of noconsequence. This contact strip of relatively stiff metal may be bentaround the end of the spring as will be readily understood.

Spring l5 may be constructed of resilient bior multi-metallic sheet,whereby the switch will be displaceable by temperature change ratherthan by pressure application. In this case, the pin or button I I isomitted, the actuating pressure or displacement being produced byinternal strain of the bior multi-metallic sheet due to the differentthermal expansion of the components thereof in a manner well understood.The thermostatic metal used may be a standard conventional bi-metalliccombination. The metal is properly tempered to insure sufficientspringiness for member i5. Upon a predetermined tem perature rise, thethermostatic metal of the switch causes a distortion and internalpressure or strain in the body thereof to fiip the switch to itsopposite or heated position.

In Figures 8 and 9 there is shown another switch construction accordingto the invention comprising a flat spring 28 having an aperture 29 toform a frame mounted in fixed position at one side in any suitablemanner such as by means of screw bolts or rivets passing throughmounting holes 30. The portion of the frame opposite to its supportedside is provided with a pair of transverse grooves or crimps 3| and 3|causing the outer free regions 32 and 32' to assume a curved or 'bentshape towards one side from wh ch they may be displaced to a position ofopposite curvature with a snap action by a slight pressure applicationor thermally produced slight displacement of the central region .1between the crimps 3| and 3| in a manner readily understood from theforegoing. Contacts 33 and 33' are secured to the outer free ends of thespring member and cooperate with one or more stationary contacts 34 and34.

It wll be evident from the foregoing that the invention is not limitedto the specific construction and details described and disclosed forillustration and that the underlying novel principle of the invent onwill be susceptible of numerous variations and modifications comingwithin the broader scope and spirit thereof as defined in the appendedclaims. The specification and drawing are, accordingly, to be regardedin an illustrativerather than in a limiting sense.

I claim:

1. In a snap action device, a body member, an actuating memberconstituted by a flat rectangular leaf spring of substantially eventhickness throughout and provided with at least one longi tudinal slotand having one of its short ends fixedly secured to said body membercantilever fash ion, the portion of said spring adjacent to said slotbeing substantially fiat and the portion between the outer end of saidslot and the adjacent free end of 'said spring being crimped to producea biased region near the fixed end of said spring, whereby the free endof said spring will move from one to another position with a snap actionover a relatively large distance by comparatively small displacement ofsaid biased region.

2. In a snap action device, a body member, an actuating memberconstituted by a fiat leaf spring of substantially even thicknessthroughout and provided with at least one longitudinal slot and havingone end fixedly secured to said body member cantilever fashion, theportion of said spring adjacent to said slot being substantially fiatand the portion between the outer end of said slotand the adjacent freeend of said spring being deformed by at least one groove-like crimpsubstantially parallel to said slot to produce a biased region near thefixed end of said sprin whereby the free end of said .spring will movefrom one to another position with a snap action upon comparatively smalldisplacement of said biased region.

8. In a snap action device, a body member, an actuating memberconstituted by a flat leaf spring of substantially even thicknessthroughout and provided with at least one narrow slot terminating in anenlarged aperture and having its end opposite to said aperture fixedlysecured to said body member cantilever fashion, the portion of saidspring adjacent to said slot being substantially fiat and the portionbetween said aperture and the free end of said spring being deformed byat least one groove-like crimp substantially parallel to said slot toproduce a biased region near the fixed end of said spring, whereby thefree end of said spring will move from one to another position with asnap action over a relatively large distance by comparatively smalldisplacement of said biased region.

4. In a snap action device, a body member, an actuating memberconstituted by a fiat leaf spring of substantially even thicknessthroughout and provided with at least one longitudinal slot terminatingin an enlarged aperture spaced from an edge of said spring, said springhaving its end opposite to said aperture fixedly secured to said bodymember cantilever fashion, the portion of said spring adjacent to saidslot being substantially fiat and the portion between said aperture andthe adjacent free edge of said spring being deformed by at least onegroove-like crimp substantially parallel to and in line with said slotto produce a biased region adjacent to the fixed end of said spring,whereby the free end of said spring will move from one to anotherposition with a snap action overa relatively large distance upon arelatively small displacement of said' biased region.

5. In a snap action device, a body member, an actuating memberconstituted by a fiat leaf spring of substantially even thicknessthroughout and provided with atleast one longitudinal slot terminatingin an enlarged aperture spaced from the adjacent edge of said spring,said spring having its end opposite to said aperture fixedly securedupon said body member cantilever fashion, the portion of said springadjacent to said slot being substantially fiat and the portion betweensaid aperture and the outer free edge of said spring being provided witha pair of groove-like crimps located symmetrically and substantiallyparallel to said slot to produce a biased region near the fixed end ofsaid spring, whereby the free end of said spring will move from one toanother position with a snap action over a relatively large distanceby'comparatively small displacement of said biased region.

6. In a snap action device, a body member, an actuating memberconstituted by a flat leaf spring of substantially even thicknessthroughout and provided with a T-shaped aperture comprising alongitudinal slot extending over a substantial length of said spring andterminating in a transverse slot. means for fixedly securing the end ofsaid spring opposite to said transverse slot to said body member, theportion of said spring adjacent to said slot being substantially flatand the portion between said transverse slot and the adjacent free endof said spring being deformed by a pair of groove-like crimps arrangedsymmetrically and substantially parallel to said longitudinal slot toproduce a biased region near the fixed end of said spring, whereby thefree end of said spring will move from one to another position with asnap action over a relatively large distance by comparatively smalldisplacement of said biased region.

7. In a snap action device, a body member, an actuating memberconstituted by a flat leaf spring of substantially even thicknessthroughout and provided with a pair of parallel longitudinal slots,means for fixedly securing one end of said spring to said body membercantilever fashion, the portion of said spring adjacent to said slotsbein substantially fiat and the portion between the outer ends of saidslots and the free end of said spring being deformed by groove-likecrimps substantially parallel to said slots to produce a biased regionadjacent to the fixed end of said spring, whereby the free end of saidspring ,will move from one to another position with a snap action over arelatively large distance by comparatively small displacement of saidbiased region.

8. In a snap action device, a body member, an actuating memberconstituted by a fiat leaf spring of substantially even thicknessthroughout and provided with a, longitudinal slot extending over a.considerable length thereof, means for fixedly securing one-end of saidspring to said body member cantilever fashion, the portion of saidspring adjacent to said slot being substantially flat and the portionbetween the outer end-of said slot and the free end of said spring beingdeformed by at least'one groove-like crimp substantially in line withsaid slot to produce a biased region near the fixed end of said spring,whereby relatively small displacement of said biased region causes acomparatively large displacement of the free end of said spring betweentwo positions with a snap action.

WILLIAM DUBILIER.

